SerpApi.Org
Scientists have identified the type of space rock that wiped out the dinosaurs — and it is one of the rarest kinds of meteorite known. A new study concludes the asteroid was a CO chondrite: a class so scarce it makes up only a tiny fraction of the five percent of meteorites sampled on Earth. The finding does not change the broad story. But it does shift our understanding of how the impact killed so much life.
Researchers from VUB and the University of British Columbia, alongside teams in Paris and Vienna, analyzed nickel isotopes from the global clay layer left behind by the Chicxulub impact — a thin geological scar found in rocks worldwide.
Nickel atoms trapped in 66-million-year-old clay held the answer
Different types of meteorites have distinct nickel isotope fingerprints. By matching the isotopes in the clay to known meteorite classes, the team could narrow down what the impactor was made of.
It was not simple work. When the asteroid struck, it vaporized almost entirely on impact. Only microscopic traces survived in the clay. Researchers had to measure those traces with extreme precision.
Their analysis pointed to one group: carbonaceous chondrites of the Ornans class, or CO chondrites. “Carbonaceous chondrites of the Ornans class are definitely not like the typical meteors you find in museum collections,” said Professor Philippe Claeys of VUB and UBC. A 2024 study had already used ruthenium isotopes to show the impactor was broadly carbonaceous. This new work narrows the identification much further.
It had far less sulfur than scientists assumed
CO chondrites contain far fewer volatile elements than other meteorite types — less carbon, zinc, water and, crucially, less sulfur. That distinction matters.
Many models have suggested that sulfur from the impactor drove catastrophic climate cooling after the strike. But if the asteroid carried roughly half the sulfur of other leading candidates, its own chemistry was not the primary killer.
“It doesn’t alter our theory of what caused the extinction event,” Claeys said. “But it makes it less likely that sulfur contained in the impactor was the smoking gun. The fine debris thrown into the atmosphere would have been the primary factor.”
It was the vast cloud of dust that blocked the sun, collapsed food chains and drove the mass extinction — not gases released by the asteroid itself.
An incredibly rare visitor from the outer solar system
The Chicxulub impactor was roughly 6 to 9 miles wide. It struck the Yucatan Peninsula at around 40,389 miles per hour and carved a crater now buried beneath Mexico. The impact wiped out about 75 percent of all species, including all non-flying dinosaurs.
CO chondrites are among the most primitive materials in the solar system, barely changed since the solar system formed. They are thought to originate from distant regions far beyond Jupiter.
“Being impacted by such a rare, distant projectile really underscores how unlucky the dinosaurs were,” Claeys said. The species that had dominated the planet for 165 million years was not wiped out by a common space rock. They were killed by one of the most unusual objects in the entire solar system.
The findings were first published in Science Advances.
